Observation of the quantum Hall effect in epitaxial graphene on SiC(0001) with oxygen adsorption

TL;DR

This study demonstrates the observation of the quantum Hall effect in epitaxial graphene on SiC(0001) with oxygen adsorption, revealing low electron density and the ability to restore doping levels via vacuum annealing, which is relevant for advanced electronic applications.

Contribution

It provides experimental evidence of the quantum Hall effect in oxygen-adsorbed epitaxial graphene and shows how doping levels can be controlled through annealing.

Findings

Quantum Hall effect observed at filling factor ~2.

Oxygen adsorption reduces carrier density.

Vacuum annealing restores intrinsic doping levels.

Abstract

In this letter we report on transport measurements of epitaxial graphene on SiC(0001) with oxygen adsorption. In a $50\times 50 \mu\mathrm{m^2}$ size Hall bar we observe the half-integer quantum Hall effect with a transverse resistance plateau quantized at filling factor around $\nu = 2$, an evidence of monolayer graphene. We find low electron concentration of $9\times 10^{11} \textrm{cm}^{-2}$ and we show that a doping of $10^{13}\textrm{cm}^{-2}$ which is characteristic of intrinsic epitaxial graphene can be restored by vacuum annealing. The effect of oxygen adsorption on carrier density is confirmed by local angle-resolved photoemission spectroscopy measurements. These results are important for understanding oxygen adsorption on epitaxial graphene and for its application to metrology and mesoscopic physics where a low carrier concentration is required.